The 9800X3D is the best gaming CPU at the moment, so if the budget is there that’s what I’d recommend, but low supplies are keeping it OOS.
You can save a little by taking the RAM down to 6000MHz, as there‘s no significant performance with faster RAM other than in edge cases.
There‘s no need...
What do you mean by "ive sent them the specs and would love to order this on the 30th"?
PCS don't fit parts that aren't on the configurator, and as far as I know there's no LianLi fans or tryx coolers on it. There's also no white ROG Strix X870-A motherboard, nor ANY 5090s listed, nor 6000MHz...
It's a relatively underpowered GPU for 1080p gaming, never mind if you're trying to run it at the native 1440p/165Hz.
But newer laptops with newer GPUs are due a refresh, so you may get more for your money by waiting (if you can).
A 40-series is no more 'upgradable' than a 30-series...as long as the PC has an adequate PSU to sufficiently power it.
As to prices, we'd assume prices will come down...but it's pure guesswork when, by how much, and whether they'll be VFM.
Are you looking for a PCSpecialist build, or are you asking about self-builds again?
£700-£900 will not get you a ‘decent gaming PC’ as a decent 1080p G0U may cost £500 on its own…and other than mobile/NUC chips, Intel i7 processors are not, and have not been 4-core for a long time - possibly...
I’ve got Belkin and Duronic ones, but Argos, Curry’s, Amazon will have what you’re afte…and you could pick up one in the morning.
https://www.currys.co.uk/search?q=Surge%20protector
https://www.argos.co.uk/search/surge-protector/
https://www.amazon.co.uk/gp/product/B000OV0CEY/